Update Feb 5: Scott Westerfeld's article in the Guardian (UK) summarizes the whole contretemps in one easy to digest article.
Update Feb 4: Truepenny's blog is a great starting point for an update on what's been happening. It includes commentary and links to a follow up letter from Macmillan CEO John Sargent; and an excellent post from Joseph E. Lake Jr. explaining all the people involved in getting one of his books to print and the stages it goes through - which in turn explains why ebooks don't have a much cheaper cost basis than printed books.
Feb 1 2010: For those looking for a quick catchup on the Amazon-Macmillan fight I suggest these three starting points:
The open letter from Macmillan CEO John Sargent on Jan 30:
John Scalzi's post giving the author's point of view.
The Association of Authors' Representatives response as reported in Publishers Weekly.